The DNA topoisomerase I binding protein topors as a novel cellular target for SUMO-1 modification: characterization of domains necessary for subcellular localization and sumolation.

Over the past years, modification by covalent attachment of SUMO (small ubiquitin-like modifier) has been demonstrated for of a number of cellular and viral proteins. While increasing evidence suggests a role for SUMO modification in the regulation of protein-protein interactions and/or subcellular localization, most SUMO targets are still at large. ...
In this report we show that Topors, a Topoisomerase I and p53 interacting protein of hitherto unknown function, presents a novel cellular target for SUMO-1 modification. In a yeast two-hybrid system, Topors interacted with both SUMO-1 and the SUMO-1 conjugating enzyme UBC9. Multiple SUMO-1 modified forms of Topors could be detected after cotransfection of exogenous SUMO-1 and Topors induced the colocalization of a YFP tagged SUMO-1 protein in a speckled pattern in the nucleus. A subset of these Topors' nuclear speckles were closely associated with the PML nuclear bodies (POD, ND10). A central domain comprising Topors residues 437 to 574 was sufficient for both sumolation and localization to nuclear speckles. One SUMO-1 acceptor site at lysine residue 560 could be identified within this region. However, sumolation-deficient Topors mutants showed that sumolation obviously is not required for localization to nuclear speckles.
Mesh Terms:
Active Transport, Cell Nucleus, Bacterial Proteins, Binding Sites, Carrier Proteins, Cell Compartmentation, Cell Nucleus, Cell Nucleus Structures, DNA-Binding Proteins, Eukaryotic Cells, Hela Cells, Humans, Ligases, Luminescent Proteins, Mutation, Neoplasm Proteins, Nuclear Proteins, Protein Structure, Tertiary, SUMO-1 Protein, Transcription Factors, Ubiquitin-Conjugating Enzymes, Ubiquitin-Protein Ligases
Exp. Cell Res.
Date: Oct. 15, 2003
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